-- в значении She enjoys playing the piano --
Be fond of - to like someone or something very much; to like doing something:
She was very fond of horses.
My brother is fond of pointing out my mistakes.
Take pleasure in:
Why do so many boys take pleasure in torturing insects and small animals?
Be keen on- very interested, eager, or wanting (to do) something very much:
She's keen on (playing) tennis.
Delight in - to enjoy something (esp. doing something annoying to someone else):
My brother always delights in telling me when I make a mistake.
Relish - to like or enjoy something:
I enjoyed our vacation, but didn’t relish the twenty-hour trip back home.
-- If you relish the idea or thought of something, you feel pleasure that it is going to happen:
She's relishing the prospect of studying in Bologna for six months.
I don't relish telling her that her son has been arrested.
I always relish a challenge.
Revel in - to enjoy something very much:
She is revelling in the adulation of the media (macmillandictionary.com)
He reveled in his success.
-- в значении Enjoy oneself --
Have a good time… (эти два выражения, думаю, не требуют примеров)
Make merry - to have fun; to have an enjoyable time:
The guests certainly made merry at the wedding.
The children were making merry in the backyard (idioms.thefreedictionary.com)
Let one’s hair down - to allow yourself to behave much more freely than usual and enjoy yourself:
Oh let your hair down for once!
У The Bealtes в песне I’ve got a feeling есть строчка: Everybody had a good year, Everybody let their hair down.
Слова я взял из Oxford Dictionary of Synonyms, формулировки и примеры – из Cambridge Dictionary (другие источники указаны в скобках).
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